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In order to determine the role of tilt testing in the aetiological diagnosis of syncope unexplained by electrophysiological investigation, the authors retrospectively studied the results of this test in 275 patients with a mean age of 64 +/- 16 years. These 275 patients were divided into two groups: group I: 43 patients with a mean age of 50 +/- 19 years presenting with vagal syncopes, group II: 232 patients with unexplained syncope, probably vagal: group IIa (120 patients, mean age: 67 +/- 15 years), sudden syncope: group IIb (112 patients, mean age: 67 +/- 13 years). The electrophysiological investigation was inconclusive in every case. In group II, 50% of tilt tests were positive (19% under basal conditions, 31% after isoproterenol), with 61% of positive tests in group IIa, including 31% on the basal test, and 38% of positive tests in group IIb, including 11% on the basal test. In group I, 84% of tests were positive (33% on the basal test, 51% after isoproterenol), indicating a sensitivity of the test of 84%. In 96 patients with a doubtful electrophysiological investigation, the tilt test was positive in 70% of cases, allowing specific treatment or a pacemaker to be avoided in the majority of cases. 84% of vasovagal syncopes were therefore confirmed by tilt testing; 50% of syncopes unexplained by electrophysiological investigation were demonstrated to be of vasovagal origin. The author emphasize the value of tilt testing in certain discordant situations in which the clinical context is disturbing and/or electrophysiological investigation is not completely reassuring.

The authors report four observations: three are essentially clinical cases where sustained rate dependent left bundle branch block can induce syncope, where as there is no syncope when the same supraventricular tachycardia at the same frequency has narrow QRS complexes. The fourth case demonstrates the dramatic decrease of arterial electrophysiological slowly accelerated atrial pacing in a patient investigated for a loss of consciousness of unknown origin. The hemodynamic impairment due to intermittent left bundle branch block has been demonstrated even in patients with normal ventricular function. If there are critical hemodynamic events such as during fast supraventricular rhythms occurrence of a left bundle branch block may determinate a dramatic decrease of arterial pressure with syncope. Syncope of supraventricular tachycardias might be induced not only by very fast rate but also by functional left bundle branch block. It might have some interesting applications in the diagnosis of syncope when coexist electrophysiological data of supraventricular arrhythmia substrate and frequency dependent left bundle branch block.

Thirty-two complete bundle branch blocks were observed during 16,500 exercise stress tests between 1973 and 1988: there were 7 right bundle branch blocks and 25 left bundle branch blocks. Exercise stress testing was indicated in 15 cases for stable angina, in 15 cases for different functional disturbances and in 2 cases as a systematic investigation. All patients underwent coronary angiography and selective left ventriculography. Right bundle branch block occurring at a heart rate of 105 +/- 25/mn were associated with typical anginal pain at the time of apparition in 5 patients. Coronary angiography showed triple vessel disease in 3 cases, double vessel disease in 2 cases and an isolated proximal lesion of the left anterior descending artery in 2 cases. Left bundle branch block occurring at a heart rate of 125 +/- 12/mn was associated with normal coronary angiography in 7 cases. Eighteen patients had pathological coronary angiogrammes with severe lesions of the left anterior descending artery. Two women suffered from chest pain when the block developed and coronary angiography was normal in one of them. During follow-up (average 62 months), 16 coronary events were observed including 2 infarcts, and 6 patients developed cardiac failure. In conclusion, complete right bundle branch block appearing during exercise stress testing was constantly associated with atherosclerotic coronary artery disease. The predictive value of complete left bundle branch block on effort was 72%. Complete left bundle branch block occurring at heart rates of less than 120/mn was frequently associated with a proximal stenosis of the left anterior descending artery.